1. Field of the Invention
The present invention relates to a method for screening an ingredient which is to be applied to the hair; a kit for carrying out the screening; and a composition comprising an ingredient exhibiting effects to accelerate absorption of an active ingredient through skin pores (hereinafter the absorption will be referred to as “skin-pore absorption”) and transfer of the active ingredient to sebum, the effects being confirmed by means of the screening method.
2. Background Art
An important step in the development of a hair-growing agent is to confirm that an active ingredient exhibits excellent hair-growing effect and has penetrability so as to reliably reach a target site. Whether or not the active ingredient reliably reaches the target site greatly depends on the properties of the active ingredient or the base ingredient of the hair-growing agent.
The mechanism of absorption of a drug or an active agent through hair follicles has become of interest, since hair follicles are considered to be an effective route through which a hair-growing agent as well as a vaccine or a gene can be administered.
The degree of transfer of a drug to sebum (hereinafter the degree will be referred to as “sebum transferability”) has been reported to influence whether the drug easily reaches a target site in the skin (e.g., hair follicles or sebaceous gland) (Critical Reviews, 14 (3): 207 219 (1997)).
The penetrability of a drug through the hair follicles has been studied, for example, by the following methods:
(1) a method for observing tissue sections by means of fluorescence labeling or radioisotopes (Suzuki, M., et al., J. Soc. Cosmet. Chem. (1978), Nicholau, G., et al., Xenobiolica (1987), Lieb, L. M., et al., J. Invest. Dermatol. (1995)) and
(2) a method for comparing hairy skin and hairless skin with respect to the transdermal permeability of a drug (e.g., comparison of hairless rat and hairy rat: Illel, B., et al., J. Pherm. Sci. (1991); comparison of normal human skin and skin which has received burns and has subsequently healed: Hueber, F., et al., J. skin Pharmacologic. (1994)).
However, method (1) is qualitative rather than quantitative, and the method involves the time-consuming preparation of tissue sections. In method (2), absorption of a drug is studied only from the viewpoint of transdermal absorption, and “skin-pore absorption” and “sebum transferability,” which are important properties of a hair-growing agent, cannot be confirmed directly.
Therefore, the aforementioned conventional methods encounter difficulty in directly confirming that a drug reaches a target site in the skin and exerts the intended effects.